net/core: Add drop counters to VF statistics

Modern hardware can decide to drop packets going to/from a VF.
Add receive and transmit drop counters to be displayed at hypervisor
layer in iproute2 per VF statistics.

Signed-off-by: Eugenia Emantayev <eugenia@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>

include/uapi/linux/if_link.h

@@ -732,6 +732,8 @@ enum {
 	IFLA_VF_STATS_BROADCAST,
 	IFLA_VF_STATS_MULTICAST,
 	IFLA_VF_STATS_PAD,
+	IFLA_VF_STATS_RX_DROPPED,
+	IFLA_VF_STATS_TX_DROPPED,
 	__IFLA_VF_STATS_MAX,
 };